Connection system between a spinal rod and a transverse bar

ABSTRACT

A system for connecting a spinal osteosynthesis rod and a crossbar include a passage for receiving the corssbar and hinge mounted jaws for clamping the rod. A locking device biases the crossbar against the jaws. A return spring pulls the jaws relatively close to one another independently of the crossbar such that the jaws may clamp the osteosynthesis rod to ensure a stable mounting of the connection system to the osteosynthesis rod.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of International Application No.PCT/FR03/00425 filed Feb. 11, 2003, which claims priority to FrenchApplication No. 02/01626 filed Feb. 11, 2002 both of which are herebyincorporated herein in their entireties by reference.

FIELD OF THE INVENTION

This invention concerns the technical area of osteosynthesis in thegeneral sense and covers, in particular, devices that permit anintervertebral connection capable of stabilizing the spine or correctingdeformations of the spinal column.

BACKGROUND OF THE INVENTION

This invention more particularly covers the area of systems capable ofproviding a connection between a spinal osteosynthesis rod and acrossbar.

In the state of the art, there are a number of known intervertebralconnecting devices. In a conventional way, such a device includes boneanchoring elements such as, for example, peduncular implantation screwsor vertebral hooks, each equipped with an attachment head for aconnection rod joining these elements together. The bone anchorageelements are distributed along the area of the spinal column to betreated to permit the mounting of two connection shafts extending moreor less in parallel to one another on either side of the spinalapophyses of the vertebrae. At least one cross strut between theconnection rods is advantageously used to stabilize and/or achieve acorrective effect on the arrangement made (either in relaxation or incompression).

Different types of connection systems between an osteosynthesis rod anda crossbar have been proposed in the prior art. For example patent FR 2745 708 describes a connection system consisting of a first jaw-shapedpart with a channel for the crossbar and a lock screw that can extendinto the channel, and a second part in the form of an opposing jawhinged onto the first part. The channel is adapted to receive thetransversal connection part which, when the screw is tightened, can cometo rest against the first and second parts in order to bring the jawstogether. Such a connection system has the advantage of being able to beadapted directly to spinal osteosynthesis rods at any point on the rods,except of course the installation sites of the peduncular screws andhooks. Moreover, the jaws of this system partially surround theosteosynthesis rod, which prevents local intervention on the vertebraeto clear the space needed to install this connection system.

However, it must be noted that the operation of installing this systemconnecting a crossbar and an osteosynthesis rod is very difficult tocarry out properly. Indeed, one must recognize that the connectingsystem must be maintained on the osteosynthesis rod while making surethe crossbar slides through the reception channel. Maintenance of thesystem must be pursued in order to permit a slight tightening of thelock screw to make sure the connection system remains in position whileretaining overall mobility in order to install another connection systemat the opposite end of the crossbar.

To try to offset these drawbacks, document FR 2 771 918 proposed aconnector for a spinal osteosynthesis device made in the form of asingle piece designed to present two jaws extending by means ofconnections from a head for a crossbar to pass. Given the elasticity ofthe material and the slots made at the connections, the two jaws rotatefreely to tighten the osteosynthesis rod. This connector is thereforeclamped onto the rod before the crossbar is installed. However, theconnector is adapted to the rod with a clamping force that is difficultto control given the way the jaws are made. It is therefore difficult toinstall and position the connector on the rod.

To achieve this objective, the connection system between a spinalosteosynthesis rod and a crossbar is set up in such a way as to offer achannel for the crossbar that is designed to exert an effort on two jawshinge-mounted so as to make sure they will come together when a lockingdevice is tightened. According to the invention, the connection systemincludes a common hinge pin to which the jaws are attached and a returnspring mounted so as to work on the two jaws to bring them relativelyclose together independently of the crossbar in such a way that the jawsclamp the osteosynthesis rod in order to ensure the stable mounting ofthe connection system onto the said rod.

SUMMARY OF THE INVENTION

According to a preferred embodiment of the invention, the connectionsystem includes a means for limiting how close the jaws come toward oneanother under the action of the return spring so that they form betweenthem, when they are the closest to one another a coupling channel forthe osteosynthesis rod such that when a thrusting effort is applied tothe jaws when in the rest position on the osteosynthesis rod, the jawsopen to enclose and clamp onto the rod so that the connection system isfastened to the rod.

A number of other characteristics emerge from the description givenabove with reference to the attached drawings which show, asnon-limiting examples, some forms of embodiment and implementation ofthe object of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial perspective view showing a spinal connection deviceequipped with connection systems according to the invention.

FIG. 2 is a front view of a connection system according to theinvention.

FIG. 3 is a perspective of a connection system according to theinvention, from which a portion has been torn away.

FIG. 4 is a front view showing the connection system between anosteosynthesis rod and a crossbar.

FIG. 5 is a top view of a connection system according to the invention.

FIG. 6 is a perspective of another variant form of embodiment of aconnection system according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout, and prime notation is used toindicate similar elements in alternate embodiments.

Referring initially to FIG. 1, FIG. 1 is a partial representation of anintervertebral connection device 1 including two spinal osteosynthesisrods 2 each of which has a circular cross-section and is designed to befastened onto vertebrae by means of bone anchorage elements not shownbut known in themselves, such as peduncular screws or hooks.

The purpose of the invention is a connecting system 3 between theosteosynthesis rod 2 and a crossbar 4 which has, for example, arectangular cross-section. In the example illustrated, the crossbar 4 isintended to provide bracing between the two osteosynthesis rods 2 suchthat each end of the crossbar 4 is assembled to a rod 2 through aconnection system 3 according to the invention.

The connection system 3 according to the invention includes a first jaw5 and a second jaw 6 opposing the first jaw forming a clamp or clipintended to be mounted onto an osteosynthesis rod 2. As more preciselyshown in FIGS. 2 to 4, each jaw, 5, 6 has a general profile that can beassimilated to a triangle. Thus, each jaw 5, 6 has a support plate 7,extending to the outside through a groove 8 connecting to a convex outersurface 9. Each jaw 5, 6 also includes a clamping surface 11 with aconcave profile that is connected to the outer surface 9 by one extremeedge 12. Each jaw 5, 6 therefore has a tapered profile that limits itssize.

The jaws 5, 6, which are made of two separate parts, are hinge-mountedonto a common hinge pin 14 and are turned to face one another. To thatend, each jaw 5, 6 has a pair of brackets 15 each one having a hole init to allow passage of the common hinge pin 14. The pairs of brackets 15are installed at the level of a connecting zone 16 between the clampingsurface 11 and the support plate 7. The pair of brackets 15 of one jawextends symmetrically with respect to the pair of brackets of the otherjaw. In addition, the pairs of brackets 15 protrude from the connectionzone 16 of the jaws in such a way as to be interpenetrated in order topermit alignment of the holes through which the hinge pin 14 passes.

According to one characteristic of the invention, the connection system3 includes at least one return spring 20 that pulls the jaws 5, 6 towardone another in a relative way, in other words, so they can close so thatthe jaws 5, 6 will clamp onto the osteosynthesis rod 2 in order toensure the stable installation of the connection system on said rod 2.The return spring 20 is a part separate or independent of the jaws 5, 6and is mounted in such a way as to press on the two jaws 5, 6 in orderto bring them relatively closer to one another. In the exampleillustrated, the return spring 20 consists of a coil spring engaged onthe hinge pin 14, each of whose ends 20, rests in a notch 22 made fromthe support plates 7 of the jaws. The return spring 20 is thereforeseated between the two jaws 5, 6 in the notch 22 created between the twojaws. Of course, the return spring 20 could be made in a differentmanner, for example, in the form of a leaf spring.

To the extent the jaws 5, 6 are symmetrical with respect to the hingepin 14, the tightening effort exerted on the rod by the jaws issymmetrically opposed by being extended to the two opposing surfaces ofthis rod. It must be recognized that this clamp or clip formed by thetwo jaws 5, 6 is capable of being installed on rods that have diametersof different values while effectively clamping the rod. According to apreferred exemplified embodiment, the clamping surface 11 of each jaw 5,6 consists of bearing surfaces 11 ₁ and 11 ₂ of different cross-sectionsin order to improve the surface contact with the rod in terms of thediameter of the rods 2. It should be noted that the dimensioning of thejaws 5, 6 is adapted so that when in clamping position on the rod 2,their outside edges 12 are at all times set back with respect to a planepassing through the external generatrix of the rod 2. The jaws 5, 6 thuspartially surround the rod 2.

The connection system 3 also includes a mounting support 25 for the jaws5, 6. As more clearly appears in FIGS. 1 and 2, the support 25 is in theform of a caliper comprising a cap 26 extended on both sides by jamb 27at each end of which there is a borehole 28 to receive one end of thehinge pin 14. The jambs 27 and the jaws 5, 6 are designed so as topermit the movement of the jaws so they can clamp onto the rod 2. Tothat end, each jaw 5, 6 has at the level of its area of connection 16, aclearance channel 30 created starting from the support plate 7 andopening onto the side faces of the jaws.

According to a preferred exemplified embodiment, the connection system 3includes a means 33 for limiting how close the jaws 5, 6 come togetherunder the action of the return spring so that they will form betweenthem, when they are closest to one another, as shown in FIG. 2, achannel 34 for engagement of the osteosynthesis rod 2 so that when athrusting effort is exerted on the jaws resting on the rod 2, the jawsopen to enclose and clamp onto the rod. When they are in this positionof maximum closeness, the outside edges 12 of the jaws are separated soas to permit the gradual opening of the jaws so that the rod 2 can beengaged between the jaws 5, 6 where it will be clamped and theconnection system 3 will be fastened onto the rod.

In the exemplified embodiment illustrated, the means for limiting howclose the jaws come together 33 consists of stops 36 created by the edgeof the jambs 27 on which a back wall 37, limiting the clearance 30,comes to rest. It is clear that the jaws 5, 6 in rest position areworked on by the return spring 20 until they are as close as possible,this position corresponding to the resting of the jaws 5, 6 against thestops 36.

According to another preferred exemplified embodiment, the connectionsystem 3 includes a means 40 for limiting the separation of the jaws 5,6 under the action, in particular, of an untimely separating effort ofthe jaws 5, 6 in order to prevent damage to the return spring 20. Thismeans of limiting the separation 40 consists of the edge 41 of the jambs27 on which the back wall 37 of the jaws can come in contact. Theconnection system 3 also includes a passage 45 for the crossbar 4. Inthe exemplified embodiment illustrated in the drawings, the passage 45is delimited in part by the support 25, in other words by the internalfaces of the jambs 27 and of the cap 26 and by the support plate 7 ofthe jaws. This passage 45 includes a rectangular cross-section orientedalong an axis substantially orthogonal to the hinge pin 14 of the jaws5, 6.

The connection system 3 also includes a clamping device 48 such as ascrew that extends inside the passage 45. This lock screw 48 is screwedinto an internal screw thread on the cap 26 in such a way as to beaccessible from the outside face of the cap 26 (FIG. 5).

The implementation of a connection system 3 between an osteosynthesisrod 2 and a crossbar 4 flows directly from the preceding description.

After the installation of a spinal osteosynthesis rod according to knowntechniques, the connection system 3 can be stably assembled to said rod2 at the desired point. In that connection, the connection system,generally without the crossbar 4, is shifted by means of aspecially-adapted ancillary device, in a direction substantiallyperpendicular to the axis of the rod, by orienting the extreme edges 12of the jaws toward the osteosynthesis rod 2. As more specificallyindicated in FIG. 2, the connection system 3 is moved in the directionof the arrow f₁. During this movement, the jaws 5, 6 rest on the rod 2in such a way that pursuing the thrusting effort in the direction f₁leads to the gradual opening up of the jaws which then enclose and clamponto this rod. It should be noted that the opening of the jaws 5, 6occurs automatically and easily due to the presence of the clearancechannel 34 made between the outside edges 12 of the jaws. Afterelimination of the thrusting effort, the jaws 5, 6 exert, under theaction of the return spring 20, sufficient clamping effort around therod 2 to permit it to be stably mounted onto the rod 2 without outsideintervention.

The stable positioning of such a connection system 3 onto the rod 2facilitates the subsequent operation of inserting the crossbar 4 intothe passage 45. Of course, in the event a crossbar 4 is placed betweentwo osteosynthesis rods 2, an identical operation involving the mountingof a connection system 3 pursuant to the invention is carried out on theother osteosynthesis rod. As more precisely illustrated in FIG. 5, itshould be noted that the width of the passage 45 is greater than thewidth of the bar 4 to permit the angular clearance of the bar withrespect to the rod 2.

After the positioning of the crossbar 4, the locking screw 48 is screwedin such a way that the bar 4 rests on the jaws 5, 6 in order to bringthem together so as to permit the rod 2 to be clamped by the jaws 5, 6.To that end, the connecting grooves 8 of the support plates extend to ahigher level with respect to the hinge pin 14, making it possible forthe bar to rest on these areas and then for the jaws 5, 6 to pivottoward one another.

In the example illustrated in FIGS. 1 to 5, the crossbar 4 exerts adirect effort on the jaws 5, 6 under the action of the locking screw 48.FIG. 6 shows another form of embodiment in which the bar 4 is equippedwith an opening 50 that is in contact on the support plates 7 of thejaws, which is acted upon by a locking device consisting of a nut fittedonto a threaded rod on the support 25. It should be noted that theeffort transmitted by the bar 4 to the jaws 5, 6 can be exertedindirectly through a washer placed between the jaws and the bar 4.

The invention is not limited to the examples described and represented,as various modifications can be made to same without departing from itscontext.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

1. A system for connecting a spinal osteosynthesis rod and a crossbar,the system comprising: a support having a channel for receiving acrossbar therein; jaws hingedly mounted to the support by a common hingepin for receiving an osteosynthesis rod therebetween; a return springmounted so as to bias the jaws closer to one another independently ofthe crossbar, wherein the jaws clamp the osteosynthesis rod for ensuringa stable mounting of the connection system onto the osteosynthesis rod;and a locking device operable with the support for biasing the crossbaragainst the jaws for clamping the rod therewith.
 2. A system accordingto claim 1, further comprising means for limiting how close the jaws arebrought together by the action of the return spring such as to formbetween them, when they are as close as possible, an engagement channelfor he osteosynthesis rod such that when a thrusting effort is appliedto the jaws when supported on the osteosynthesis rod, the jaws open upto enclose and clamp the osteosynthesis rod so that the connectionsystem is attached thereto.
 3. A system according to claim 1, whereinthe return spring is engaged onto the hinge pin while lodged in a notchformed in the jaws.
 4. A system according to claim 1, wherein the jawsare symmetrical, each one presenting a tightening surface with anopposing action on the osteosynthesis rod and enabling the jaws to bemounted on a plurality of ostheosynthesis rods of differing diameters.5. A system according to claim 4, wherein the jaws each include aclamping surface having a bearing surface with a differingcross-sections.
 6. A system according to claim 1, wherein the hinge pinis carried by the support such that the channel forms a passagetherethrough for the crossbar, the support being equipped with thelocking device that extends into the passage.
 7. A system according toclaim 6, wherein the passage extends in a direction substantiallyperpendicular to the hinge pin operable with the jaws, in a widthdimension greater than a width dimension greater than a width dimensionof the crossbar for permitting an angular clearance for the crossbar. 8.A system according to claim 1, further comprising stops operable withthe jaws for limiting a space therebetween.
 9. A system according toclaim 1, further comprising at least one crossbar carried by the supportfor connecting to at least one osteosynthesis rod clamped by the jaws.